Self-contained power actuator



May 22, 1956 B. N. ASHTON SELF-CONTAINED POWER ACTUATOR 2 Sheets-Sheet 1Filed Aug. 1. 1951 INVENTOR. BENJAMIN N. ASHTON ATTORNEYS United StatesPatent SELF-CONTAINED rowan ACTUATOR Benjamin N. Ashton, Kingston, N.Y., assignor to Elec'troi Incorporated, Kingston, N. Y., a corporationof Delaware Application August 1, 1951, Serial No. 239,860

2 Claims. (Cl. 66-52) This invention relates to hydraulic actuators andmore particularly to self-contained actuator assemblies adapted to beoperated by means of simplified external control circuits.

Hydraulic actuators are well known for their low cost, high'eflic'iency, rapid response characteristics and light weight, and forthis reason are widely used wherever power actuators are needed. Onelimiting factor, however, in the use of hydraulic actuators as opposedto other types of power actuators, such as electro mechanical devices,is the control system. The control of hydraulic actuators is commonlyeffected by means of a valve assembly and pressure source locatedexternally and remotely of the power converting unit itself. Hydraulicsystems for use in aircraft, for example, may utilize a central valvecontrol system for governing the flow of fluid to several actuatorslocated throughout the plane. This necessitates the close maintenance ofthe various fluid conduits and presupposes the continuing operability ofthe central system and, in many cases, of each of the remote actuators.

It has been found, however, that improved operating characteristicsincluding safety, reliability and efiiciency may be achieved byeliminating the central pressure source and control valve assembly, aswell as the numerous pressure and discharge conduits which mustnecessarily radiate therefrom.

It is accordingly one object of this invention to provide an hydraulicactuator unit embodying within one compact housing all of the basiccomponents of 'an hydraulic system.

It is another object of the invention to provide an eflicient hydraulicunit adapted to be externally controlled by means of simplifiedelectrical control circuits.

It is a further object of the invention to provide an hydraulic poweractuator assembly which is self-contained as a single unit and which maybe Wholly controlled by means of electrical circuits or which may,alternatively, embody a control system utilizing both electrical andhydraulic control components.

In accordance with the invention an hydraulic unit may be provided whichcomprises a single housing 'having an hydraulic cylinder, an electricmotor, and a pump mounted therein as a compact assembly to be controlledexternally by means of an electric control circuit 'to the motor. Thecylinder may be fitted with limit switches whereby the system isautomatically shut oii at the completion of each stroke of a pistonwithin the cylinder, and reversing of the piston within the cylinder maybe accomplished effectively by reversing the motor and pump.

The invention further contemplates the use of accumulator means in thepressure lines for storing energy during one operation for use in alater operation, thereby to insure quick starting and lower powerrequirements at the outset of the second operation. If desired a valvesystem may be provided within the housing which is also electricallycontrolled and which facilitates 2,746,251 Patented May 22, 1956 thereversing of the movement of the piston -within 'the cylinder. In thisembodiment the electrical control circuit for the motor is simplified inthat the latter may be unidirectional.

The above and other features and objects of the .in-

ice

vention may be better understood with reference to the accompanyingdrawings in which:

Fig. 1 is a schematic diagram of an hydraulic system formed according tothe invention;

Fig. 2 is a wiring diagram of the control circuit .for the hydraulicsystem shown in the schematic diagram of Fig. 1; i

Fig. 3 is a top view of a self-contained hydraulic power actuatorembodying the electrical and hydraulic systems disclosed in Figs. 1 and2;

Fig. 4 is a view in side elevation partly in section on the line 4-4 ofFig. 3 looking in the direction of the arrows; and

Fig. 5 is a View in transverse section taken 'on the line 55 of Fig. 4looking in the direction of the arrows.

Referring to the drawings and to Figs. 1-5 in particnlar, the inventionis shown as embodied in a self-contained, hydraulic actuator 10assembled as a unit in housing or .frame 11. Generally the unit, asshown in Figs. 35,- includes an electric motor '12 connected to drive anhydraulic or gear pump 13, a check valve '14, an accumulator or storagedevice 15, a solenoid operated selector valve assembly 16, a fluidreservoir 17, and an hydraulic jack assembly 18 including a cylinder 18aformed in the 'frame 11 and having a piston 18b mounted therein for'reciprocatory sliding movement.

Referring to the schematic diagram of Fig. 1, it will be seen that thesystem is connected so that the pump :13 draws fluid from the reservoir17 through a conduit or duct 19 and discharges fluid under pressure intothe conduit 20 in which the check valve 14 is located. The conduit 20discharges into the selector valve assembly 16, which is connected toopposite ends of the hydraulic cylinder 13a by means of conduits 21 and22. The "conduits 21 and 22 are alternately used as pressure and returnlines by the action of the selector valve assembly 16 as described indetail below, and in this fashion the piston 18b may be caused to moveto and train the cylinder. The discharge from the selector valveassembly 16 is fed by a return conduit 23 to the reservoir 17. Theacclunulator 15 is connected to the pressure line "20 and a pressurerelief valve 24 is connected between the pressure and return conduits 22and 23 respectively.

The electrical control circuit for the system as diagrammed in Fig. 2includes a source of electrical energy such as a battery 24, forexample, the negative terminal of which is connected by a conductor 25to one terminal of the electric motor 12. The positive terminal of thebattery 24 is connected by a conductor 26 to a double pole, double-throwswitch 27 "having a first pair of stationary contacts 27a and 27b, and asecond pair of stationary contacts 27c and 270?. The contact 27a isconnected by a conductor 28 to one contact 29:: of a limit switch 29(see also Fig. 4) which is mounted near the hydraulic jack 18 to beactuated by the piston 1812 at the completion of each stroke. Thecontact .271) is connected to a contact 2% of the limit switch 29 by aconductor 39. The contact 270 is connected by a conductor 34 to a coil31 of the selector valve assembly 16. The coil 31 is connected to thenegative terminal of the battery 24 by the conductor 25. The contact 27dof the switch 27 is connected by a conductor 35 to a coil 36 which isalso connected to the negative terminal of the battery 24 by theconductor 25. The limit switch 29 is connected to the second terminal ofthe motor 12 by means of a conductor 33 to complete the electricalcontrol circuit.

.ment of the piston.

Referring now to Fig. 4, it will be seen that the motor 12 is bolted tothe frame 11 by bolts 34. The reservoir 17 is formed adjacent the motormounting and the pump 13 is mounted in the reservoir chamber by means ofbolts 35. The pump is coupled to the motor 12 by a shaft 36'. The pumpdraws fluid from the reservoir through an inlet 37 (Fig. and dischargesthe fluid through a duct or conduit 33 to a duct 39 (Fig. 5) which feedsthe selector valve 16. It will be recalled that the selector valvecontrols the flow of fluid from the pump selectively into either end ofthe cylinder 18a.

The discharge conduit of the pump is fitted with the check valve 14which is received in a recess 44 formed in a passage plate :41 whichbounds one end of the reservoir. The check valve 14 comprises a ball42'urged by coil spring 43 against the discharge end of the conduit 38.The conduit 38 also communicates by means of a bore 44 with theaccumulator which comprises a domeshaped cover-plate 45 bolted to thepassage plate 41 and housing a resilient, imperforate diaphragm 46 whichforms a chamber to maintain the fluid pressure substantially uniform andto store pressure for subsequent strokes of the piston.

The selector valve 16 as best seen in Fig. 5, comprises a valve stem 47received in an elongated sleeve 48 received in a through bore 48 formedin the passage plate 41. The valve stem 47 is formed with a series ofthree axially spaced cylindrical portions or slides 42, 5t and 51, whichengage the inner walls of the sleeve 48. The sleeve 48 is formed on itsouter surface with a series of five circumferential ducts 52 i 56communicating with the inner surfaces by means of radial ducts 52 56',respectively. The duct 54 communicates with the pump through ducts 39-38(corresponding to conduit 20 in Fig. 1). The duct 53 communicates with ahorizontal duct 57 which leads to an external conduit 58 which leadsthrough duct 58' (Fig. 4) to one end of the cylinder 18a. The duct 55joins an inclined duct 59 which leads to the other end of the cylinder18a. The ducts 52 and 56 both communicate with the'reservoir 17. Theseducts correspond to conduit 23 in Fig. 1.

By moving the valve stem 47 up and down, the ducts 57, 58 and 59 can bemade'to be pressure or return conduits for the cylinder, and the pistonthereby is driven in one direction or the other according. to Wellknownprinciples.

To control the selector valve, the stem 47 is elon" gated and on therespective outer ends thereof, solenoid cores 60 and 61 are mounted tobe received in the coil parts 31 and 36, described above. A fluid sealaround the selector valve is effected by the sealing rings 62'and 63,and a neutral position for the valves is effected by means of thecompression spring 64 which reacts in both directions against movementof the valve stem.

In operation, the hydraulic jack is operated by closing the switch 27for achieving the desired direction of move This completes a circuitthrough the normally closed limit switch 29 to the motor 12 which startsthe pump 13 operating to supply fluid under pressure through the conduit20 to the selector valve assembly 16. The closing of the switch 27 for adesired direction of movement of the piston energizes one of thesolenoid coils 31 or 36 of the selector valve assembly. If, for example,the piston is at the right hand end of the cylinder as viewed in Fig. 4,the selector valve stem 47 will be moved upwardly so that the fluidunder pressure from the pump enters the selector valve by means ofconduit 39 (Fig. 5) and discharges into the conduit 59, whichcommunicates with the right hand end of the cylinder. The left hand endof the cylinder is at the same time connected by means of the conduit 58and the ducts 57, 53 and 53 to the selector valve stem. The valve stemdirects the flow through ducts 52 and 52 into the reservoir 17. Thus,fluid under pressure is furnished at the right hand side of the piS'FOll18b and 4 a discharge circuit for the fluid is established at the lefthand side of the piston.

The piston will move to the left until either the switch 27 is opened orthe limit switch 29 is actuated by the arm 65' on the piston rod todeenergize the motor and stop the pump at the completion of the strokeof the piston. The piston may then be reversed and driven in the otherdirection by reversing the switch 27. This will energize the motor anddrive the pump in the same hand of rotation as in the preceding stroke,but will also energize the solenoid coil 31, causing the valve stem 47of the selector valve assembly 16 to move downwardly to establish apressure circuit from the pump through the ducts 33, 39, 54 and 54,through the selector valve to ducts 53 and 53', and to the left handside of the cylinder through the duct 57, the conduit 58 and duct 58'.At the same time a discharge circuit for the fluid back to the reservoir17 is established through the duct 59, the ducts 55 and 55 of theselector valve, ducts 56' and 56, and back to the reservoir 17. Thisstroke will continue until such time as the switch 27 is opened or thelimit switch 29 is actuated by means of a spring biased plunger 65slidably received in the cylinder head and passing through a packinggland 66. Thus, it will be understood that a highly effectivecombination of electrical and hydraulic control is provided foroperating the hydraulic jack 18 from a remote point without the use ofinterconnecting hydraulic pressure lines from the control point. Theself-contained hydraulic actuator operates independently of any externalpressure source, and provides a large degree of safety and reliabilityfor a system employing several hydraulic actuators. Failure of oneactuator unit, for example, will not result in any loss of fluid whichmight affect another actuator unit.

Thus it will be seen that a highly simplified and effective assemblydesign may be provided according to the invention for combining a pump,a motor, accumulators and an hydraulic jack into an integrated unitsusceptible of remote control solely through electrical wiring. Althougha preferred embodiment of the invention has been described above withreference to the drawings, it is to be understood that numerousmodifications may be made in the design without departing from the scopeof the invention, which should not, therefore, be limited except as setforth in the following claims.

I claim:

1. In an hydraulic system, a housing, a uni-directional electric motorcarried by the housing, a chamber in said housing forming a fluidreservoir, a pump mounted in said chamber and connected to be driven bythe motor, a cylinder formed in the housing, a piston mounted in saidcylinder for reciprocatory movement therein, a doublethrow controlswitch having a movable contact adapted to be connected to a source ofelectrical energy and a pair of stationary contacts connected to themotor, a pair of limit switches connected respectively to the stationarycontacts of the control switch and in series with the motor, said limitswitches being normally closed and adapted to be opened by movement ofthe piston to its respective extreme positions, a selector valve mountedin the housing and for controlling the flow of fluid to the cylinder,electromagnetic mean for operating the selector valve and circuit meansincluding switch means actuated with the said control switch connectingthe electromagnetic means to the said source of electrical energy.

2. Hydraulic apparatus comprising a hydraulic jack includingreciprocatable piston means, a pump, an electric motor for driving thepump, selector valve means for directing the output of the pumpselectively to opposite sides of the piston, first and secondelectromagnetic means for operating the selector valve means, a controlswitch including a double-pole, double-throw switch having a pair ofmovable contacts connected to a source of electrical energy and twopairs of stationary contacts adapted to be selectively engaged by themovable contacts, limit switch means responsive to movement of thepiston including a pair of normally closed switches each having acontact connected in series with the motor and each having a contactconnected to a corresponding stationary contact of the control switch,means connecting the first and second electromagnetic means respectivelyto the other pair of stationary contacts of the control switch, andmeans completing an electrical circuit from the electromagnetic meansand the motor to the source of electrical energy, whereby the selectorvalve may be operated by the control switch to cause the piston to bereciprocated while the motor and pump are operated in one direction onlyand whereby the motor will be deenergized by the limit switch means atthe end of each stroke of the piston.

References Cited in the file of this patent UNITED STATES PATENTS1,948,951 Walker Feb. 27, 1934 6 Hill Dec. 2, 1941 Dean July 6, 1943Piron Sept. 28, 1943 Fitch July 31, 1945 Shendrick Nov. 6, 1945 HuiferdSept. 14, 1948 Hartman Dec. 28, 1948 Patterson May 22, 1951 Livers etal. May 29, 1951 Lee July 3, 1951 Ackerrnan Sept. 23, 1952 McLeod June2, 1953 FOREIGN PATENTS Great Britain Jan. 26, 1943

